Flowering Plants - Angiosperms

Flowering Plants - Angiosperms

• Largest group of Land Plants!• Most important economically!• Apomorphies:

1. Flowers 2. Carpels3. Fruits4. Double fertilization with triploid endosperm5. Specialized conductive cells

Why have Angiosperms been so successful?

1) FlowersWhat is a flower?

= Shoot system bearing modified leaves:

PerianthCalyx (sepals) - green, protectiveCorolla (petals) - colored, attractant

Stamens - maleCarpels - female }modified

leaves

Fig. 30.7

pistil

Flower parts:

Flower pollination (transfer of pollen to ovule):

Animal pollinationAncestral for AngiospermsMuch more efficient means of transporting pollen

All Gymnosperms are wind pollinated

(Some Angiosperms secondarily wind pollinated)

Strategy of animal pollination:

AttractantVisual: large or brightly colored perianthOlfactory (smell): sweet or rotten (fetid) odor

RewardUsually nectar or pollen(Rarely waxes, oils)

Pollination MechanismsInsects

Bees Butterflies/Moths Flies

BirdsBatsWaterWind

Bee-pollinated

Moth-pollinated

Fly-pollinated

Bird-pollinated

Bat-pollinated

Wind pollination in grasses

Phyllospadix torreyiSurf-Grass

Water-pollinated

2) CarpelsCarpel = conduplicate megasporophyllConduplicate = foldedMegasporophyll = “female leaf, bearing seeds”Carpel totally encloses ovules/seeds

Carpels can fuse together

Gynoecium = all female partsPistil = ovary + style + stigma

Pistil can be one carpel or many

carpel

orange: 8 fused carpels

Function of Carpel

1. Protects young seeds

2. Site of pollen germination- Can induce self-incompatibility reactions

3. Fruits

Self-incompatibility- Pollen will not germinate on genetically similar individuals

- Promotes outcrossing

3) Fruits

Fruit = mature ovary (plus accessory parts)

Function: seed dispersal

Fruit types:

dry - dispersed mechanically, by wind, water, etc.

fleshy- dispersed by animals

4) Double fertilization in Angiosperms

Assignment:Study Figs. 38.2,

38.3, 38.5

Double fertilization in Angiosperms

Pollen produces 2 sperm cells:

Double fertilization in Angiosperms

Pollen produces 2 sperm cells:

sperm (n) + egg (n)----> zygote (2n)

sperm (n) + 2 polar nuclei (n)----> endosperm (3n)

Triploid endosperm is nutritive tissue in seeds of Angiosperms.

Extra set of genes may help in:

1) rapid development2) increase genetic variation

Gymnosperms: - Fertilization occurs long after pollination- Seeds mature slowly (1-2 years)

Angiosperms: - Fertilization occurs soon after pollination- Seeds produced rapidly- Selective advantage (e.g., annual herbs)

perforation plate

5) Specialized conductive cellsMost Angiosperms have vessels

Specialized in having perforation plates

vessel

big callose-lined

pores

All Angiosperms have sieve tube members-with sieve plates: bigger pores in end walls

AngiospermsVessels and sieve tube members

more efficient in water / sugar conduction

Angiosperm Classification

Old classification:

Dicots - 2 cotyledons (seed leaves)

Monocots- 1 cotyledon

embryo

seed coat

radicle

epicotyl

hypocotyl

2 cotyledons

endosperm

NON-MONOCOT

{

radicle

epicotyl

hypocotyl

1 cotyledon

embryo

coleorhiza

coleoptile

radicle

epicotyl

1 cotyledon

MONOCOTS

Monocotsmonophyletic

Monocot apomorphies

parallel venation

Monocot apomorphies

1 cotyledon

radicle

epicotyl

hypocotyl

1 cotyledon

embryo

coleorhiza

coleoptile

radicle

epicotyl

1 cotyledon

MONOCOTS

stem an atactostele-many scattered vascular bundles (wood lost!)

Monocots include:PalmsOrchidsIrisesGrasses, etc.

“Dicots”paraphyletic!

Features that defined “Dicots” are primitive (not apomorphies)

Eudicotsmonophyletic!

Eudicot apomorphy:

Pollen tricolpate - 3 apertures

A A

A

All other Angiosperms:

Pollen has 1 aperture

aperture

Eudicots include most angiosperms:RosesLegumesDaisiesOaks, etc.